/*
 * Copyright (C) 2015 Square, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.wrmsr.wava.java.poet;

import javax.lang.model.element.Modifier;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

import static com.google.common.base.Preconditions.checkArgument;
import static java.lang.Character.isISOControl;

/**
 * Like Guava, but worse and standalone. This makes it easier to mix JavaPoet with libraries that
 * bring their own version of Guava.
 */
final class Util
{
    /**
     * Modifier.DEFAULT doesn't exist until Java 8, but we want to run on earlier releases.
     */
    static final Modifier DEFAULT;

    private Util()
    {
    }

    static <K, V> Map<K, List<V>> immutableMultimap(Map<K, List<V>> multimap)
    {
        LinkedHashMap<K, List<V>> result = new LinkedHashMap<>();
        for (Map.Entry<K, List<V>> entry : multimap.entrySet()) {
            if (entry.getValue().isEmpty()) {
                continue;
            }
            result.put(entry.getKey(), immutableList(entry.getValue()));
        }
        return Collections.unmodifiableMap(result);
    }

    static <K, V> Map<K, V> immutableMap(Map<K, V> map)
    {
        return Collections.unmodifiableMap(new LinkedHashMap<>(map));
    }

    static <T> List<T> immutableList(Collection<T> collection)
    {
        return Collections.unmodifiableList(new ArrayList<>(collection));
    }

    static <T> Set<T> immutableSet(Collection<T> set)
    {
        return Collections.unmodifiableSet(new LinkedHashSet<>(set));
    }

    static String join(String separator, List<String> parts)
    {
        if (parts.isEmpty()) {
            return "";
        }
        StringBuilder result = new StringBuilder();
        result.append(parts.get(0));
        for (int i = 1; i < parts.size(); i++) {
            result.append(separator).append(parts.get(i));
        }
        return result.toString();
    }

    static <T> Set<T> union(Set<T> a, Set<T> b)
    {
        Set<T> result = new LinkedHashSet<>();
        result.addAll(a);
        result.addAll(b);
        return result;
    }

    static void requireExactlyOneOf(Set<Modifier> modifiers, Modifier... mutuallyExclusive)
    {
        int count = 0;
        for (Modifier modifier : mutuallyExclusive) {
            if (modifier == null && DEFAULT == null) {
                continue; // Skip 'DEFAULT' if it doesn't exist!
            }
            if (modifiers.contains(modifier)) {
                count++;
            }
        }
        checkArgument(count == 1, "modifiers %s must contain one of %s",
                modifiers, Arrays.toString(mutuallyExclusive));
    }

    static boolean hasDefaultModifier(Collection<Modifier> modifiers)
    {
        return DEFAULT != null && modifiers.contains(DEFAULT);
    }

    static String characterLiteralWithoutSingleQuotes(char c)
    {
        // see https://docs.oracle.com/javase/specs/jls/se7/html/jls-3.html#jls-3.10.6
        switch (c) {
            case '\b':
                return "\\b"; /* \u0008: backspace (BS) */
            case '\t':
                return "\\t"; /* \u0009: horizontal tab (HT) */
            case '\n':
                return "\\n"; /* \u000a: linefeed (LF) */
            case '\f':
                return "\\f"; /* \u000c: form feed (FF) */
            case '\r':
                return "\\r"; /* \u000d: carriage return (CR) */
            case '\"':
                return "\"";  /* \u0022: double quote (") */
            case '\'':
                return "\\'"; /* \u0027: single quote (') */
            case '\\':
                return "\\\\";  /* \u005c: backslash (\) */
            default:
                return isISOControl(c) ? String.format("\\u%04x", (int) c) : Character.toString(c);
        }
    }

    /**
     * Returns the string literal representing {@code value}, including wrapping double quotes.
     */
    static String stringLiteralWithDoubleQuotes(String value, String indent)
    {
        StringBuilder result = new StringBuilder(value.length() + 2);
        result.append('"');
        for (int i = 0; i < value.length(); i++) {
            char c = value.charAt(i);
            // trivial case: single quote must not be escaped
            if (c == '\'') {
                result.append("'");
                continue;
            }
            // trivial case: double quotes must be escaped
            if (c == '\"') {
                result.append("\\\"");
                continue;
            }
            // default case: just let character literal do its work
            result.append(characterLiteralWithoutSingleQuotes(c));
            // need to append indent after linefeed?
            if (c == '\n' && i + 1 < value.length()) {
                result.append("\"\n").append(indent).append(indent).append("+ \"");
            }
        }
        result.append('"');
        return result.toString();
    }

    static {
        Modifier def = null;
        try {
            def = Modifier.valueOf("DEFAULT");
        }
        catch (IllegalArgumentException ignored) {
        }
        DEFAULT = def;
    }
}
